Ukrainian officials accused Luzhkov of questioning Crimea's status as part of Ukraine.

Speaking at a joint press conference with acting Foreign Minister Volodymyr Ohryzko, Nalyvaichenko said Luzhkov could face a warning, a ban on entering the country, or more serious criminal penalties.

"A foreigner on the territory of our country, regardless of his status and citizenship, must respect the laws, the language, and the culture of the people," Nalyvaichenko said. "So, the [Ukrainian] reaction will be harsh, in accordance with the law."

Ohryzko said the Foreign Ministry and law enforcement bodies will assess the extent to which Luzhkov's comments threatened Ukraine's "territorial integrity and security."